Shear stress, often denoted by τ, is the component of stress coplanar with a material cross section. Shear stress, often denoted by τ (Greek: tau), is the component of stress coplanar with a material cross section. Shear stress, force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress. Shearing Stress is a type of stress that acts coplanar with a cross-section of material. How do we really tear paper? This seems like a silly question, but the answer is ' we shear it. Shear stress definition, the external force acting on an object or surface parallel to the slope or plane in which it lies; the stress tending to produce shear.